The titanium-iron-antimony ternary system and the crystal and electronic structure of the interstitial compound Ti5FeSb2

Phase equilibria were established in the Ti-Fe-Sb ternary system below the TiSb2-FeSb section at 1070 K; the Sb-TiSb2-FeSb region was studied at 870 K. Investigation of the phase relations was based on X-ray diffraction experiments on arc-melted bulk alloys, which were annealed up to 350 h. Four ternary compounds were observed: TiFe1-xSb (0.64≤x≤0.70; defect TiNiSi-type), Ti1.18Fe0.57Sb (partially and statistically filled Ni2In-type), Ti1+xFeSb (-0.20≤x≤0.27; transformation from defect AlLiSi-type to the defect MnCu2Al-type), and new Ti5FexSb3-x (0.45≤x≤1.00; W5Si3-type). An extended solid solution up to about 10 at.% antimony was observed for the Laves phase Ti(Fe1-xSbx)2-y. Ti3Sb seems to dissolve up to 1.4 at.% of Fe replacing titanium in the structure. At 800 deg. C there is no solid solubility of Ti in the iron antimonides and of Fe in the titanium antimonides with an Sb content higher than 25 at.%. Electronic band structure calculations indicate that Ti5FeSb2 is metallic and completely spin polarized with Fe as the carrier of the magnetic moments